Search for a scalar or vector particle decaying into Zγ in pp¯ collisions at s=1.96 TeV

We present a search for a narrow scalar or vector resonance decaying into Zγ with a subsequent Z   boson decay into a pair of electrons or muons. The data for this search were collected with the DØ detector at the Fermilab Tevatron pp¯ collider at a center of mass energy s=1.96 TeV. Using 1.1 (1.0) fb−1 of data, we observe 49 (50) candidate events in the electron (muon) channel, in good agreement with the standard model prediction. From the combination of both channels, we derive 95% C.L. upper limits on the cross section times branching fraction (σ×Bσ×B) into Zγ  . These limits range from 0.19 (0.20) pb for a scalar (vector) resonance mass of 600 GeV/c2/c2 to 2.5 (3.1) pb for a mass of 140 GeV/c2/c2.